Engagement bushing for cover panels with support core

ABSTRACT

In an engagement bushing installation for the connection of a lightweight construction panel including spaced first and second cover plates with a support layer disposed therebetween to another structure by a mounting element extending through a passage in the construction panel, the passage includes a first section which extends through the first cover plate and the support layer and a second section of smaller diameter extending through the second cover plate for accommodating the mounting element, an expansion sleeve is disposed in the first section so as to abut the second cover plate and the part of the expansion sleeve disposed in the first cover plate is radially expandable so that it can be expanded into radial engagement with the first cover plate while it is axially engaged with the second cover plate when the lightweight construction panel is engaged by the mounting element with the other structure.

This is a continuation-in-part application of pending international patent application PCT/DE2008/000257 filed Feb. 13, 2008 and claiming the priority of German patent application 10 2007 007 663.2 filed Feb. 13, 2007.

BACKGROUND OF THE INVENTION

The invention relates to an engagement bushing for the connection of a panel including a support core disposed between first and second cover sheets to a third element by means of a mounting element, wherein the bushing is provided with a through-bore for receiving the mounting element mounted to the third element.

Panels with support cores are often also called sandwich panels, honeycomb panels or lightweight construction panels. All types of panels used in furniture construction have generally cover sheets consisting of thin wood-chip plates or hard fiber boards. The sandwich panels include as center layer or, respectively, support core, for example, polyurethane foam or polystyrene. In honeycomb plates, intermediate layers, often corrugated web inserts or so-called expanded honeycomb structures, are used which have a weight of less than 500 kg/m³. If, for the intermediate layer, no fire-retardant aluminum foams or foamed glass is used, the raw density is below 350 kg/m³. For comparison, the raw density of a non-layered wood particle board is about 600-750 kg/m³.

If armatures such as handles, buttons or knobs or similar devices are to be attached to lightweight panels for examples by means of through-screws, the problem arises that the mounting elements find support only at the relatively thin cover sheets or cover plates. Mounting by way of simple through-screws is almost impossible since, upon tightening the screws, the support core yields while being plastically deformed. The cover sheets then form indentations which are clearly visible. In order to prevent the formation of indentations, the mounting means has so far generally been attached only to one of the cover plates. Among others, for optical reasons, the support core and the second cover plate can be bridged only by a sleeve.

It is the object of the present invention to provide a bushing or sleeve for lightweight construction panels mounting means which can be easily installed and permits a firm, secure and durable mounting of device on the lightweight construction panels.

SUMMARY OF THE INVENTION

In an engagement bushing installation for the connection of a lightweight construction panel including spaced first and second cover plates with a support layer disposed therebetween to another structure by a mounting element extending through a passage in the construction panel, the passage includes a first section which extends through the first cover plate and the support layer and a second section of smaller diameter extending through the second cover plate for accommodating the mounting element, an expansion sleeve is disposed in the first section so as to abut the second cover plate and the part of the expansion sleeve disposed in the first cover plate is radially expandable so that it can be expanded into radial engagement with the first cover plate while it is axially engaged with the second cover plate when the lightweight construction panel is engaged by the mounting element with the other structure.

The mounting element expands the sleeve in the opening of the first cover plate by means of a truncated cone-like or pyramid-shaped head or by means of an intermediate truncated cone or pyramid-shaped wedge element by an elastic or plastic deformation of the sleeve at least over a certain area thereof.

Preferably, the sleeve comprises an essentially tubular base body which has a planar lower and a truncated-cone-shaped upper front area wherein the imaginary tip of the truncated cone-shaped front area is disposed in the interior of the sleeve on the centerline of the sleeve and in the area of the truncated cone-shaped front, the sleeve is radially elastic or is plastically deformable and/or longitudinally slotted.

With the present invention, a sleeve is provided by which hardware fixtures or other furniture parts can be firmly and reliably mounted to lightweight construction panels. The hardware fixtures and the furniture components are mounted to the panels by means of through-screws, for example, machine screws or wood screws. After installation, the individual through-screw abuts with its head directly or indirectly the lightweight construction panel whereas the supportive thread part of the through-screw is threaded into the fixture part or respectively, the furniture part.

If appropriate, nails or rivets may be used in place of the screws.

The invention will become more readily apparent from the following description of particular embodiments thereof with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an expansion sleeve or bushing inserted into a lightweight construction panel with a screw and a handle before the mounting of the handle,

FIG. 2 shows an enlarged detail of FIG. 1 without the screw;

FIG. 3 shows the arrangement of FIG. 1 after installation of the handle,

FIG. 4 shows a detail of FIG. 3 however, enlarged,

FIG. 5 shows an expansion sleeve installed in a lightweight construction panel with a screw for threading into another plate or panel,

FIG. 6 shows the same as FIG. 5 after mounting of the plate,

FIG. 7 shows schematically the structure of FIG. 6 turned by 90° and with the panel core omitted,

FIG. 8 shows the same as FIG. 1, however with a different expansion sleeve and a different screw,

FIG. 9 shows, enlarged, a detail of FIG. 8,

FIG. 10 shows the same structure as FIG. 9 with the handle mounted,

FIG. 11 shows a detail of FIG. 10 in an enlarged representation,

FIG. 12 shows an expansion sleeve with two circumferential ribs,

FIG. 13 shows an expansion sleeve with two circumferential ribs with different flank inclinations,

FIG. 14 shows an expansion sleeve with two rows of knobs,

FIG. 15 is a top view of FIG. 14,

FIG. 16 shows an expansion sleeve with longitudinal ribs which become wider toward the end of the sleeve,

FIG. 17 is a top view of FIG. 16, and

FIG. 18 shows an expansion sleeve with a more steeply angled end wall.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

FIG. 1 shows in a cross-sectional view, a lightweight construction panel 100 with an expansion sleeve 10 disposed therein. Into the expansion sleeve 10, a mounting means 90 such as a screw is inserted in order to thread it into the thread 152 of a third element 150, for example, a handle. FIG. 3 shows the lightweight construction panel 100 with a handle 150 mounted thereto.

FIG. 3 shows, in an enlarged view, a detail of FIG. 1, wherein the expansion sleeve 10 is shown disposed in the lightweight construction panel 100, see also FIG. 11. The lightweight construction panel 100 comprises two cover sheets or plates 101 and 111 and a support core 121 disposed therebetween. Each cover plate 101, 111 consists in the shown embodiment of a thin flake board. The upper cover plate 101 has an opening 105 for example in the form of a relatively large bore whereas the lower cover plate 111 includes a smaller bore 115. The diameter of the opening 105 is for example about twice as large as the diameter of the lower bore 115.

The support core 121 is for example in the form of a foam core. It includes an opening 125 for example in the form of a bore whose diameter corresponds to the diameter of the relatively large bore 105. All bores 105, 125, 115 have a common centerline 9. The inner surfaces 103, 113 of the cover plates 101, 111 are cemented to the plate-like support core 121.

The lightweight panel 100 has a wall thickness of 15.5 mm. Each cover plate 101, 111 has a thickness of 2.95 mm. Instead of a foam core 121, the panel may include a honeycomb core.

Depending on the embodiment, the thickness of such a lightweight panel 100 is between 14 and 90 mm. The cover plates 101, 111, which, in the shown example, have the same thickness, may have a thickness in the range of 0.4 to 10 mm. The lightweight construction panels may also include several different support core layers 121 and the different support core layers may be separated by additional cover plates. The present invention is also suitable for flake board panels which include less dense intermediate layers.

The still undeformed expansion sleeve 10 is, as shown in FIGS. 2 and 11, a tubular base body 11, which consists of a plastically deformable plastic material for example a polyoxymethylene. The application-based main deformation direction extends transverse to the expansion sleeve center line 9. In the longitudinal direction, that is, parallel to the center line 9, the expansion sleeve 10 is, at least essentially, nondeformable.

The expansion sleeve 10 has a planar lower front area 15 and a truncated cone-shaped upper front face area 12. The latter is in the form of a conical counter bore. The upper front face area 12 has for example a cone-angle of 90° as it is used for commercial screws 90 with flat heads 91. The tip of the conical counter bore is disposed on the expansion sleeve center line 9 within the expansion sleeve passage 16. The wall thickness of the base body 11 is, depending on the embodiment, between 2 and 10 millimeters.

As shown in FIG. 2, the expansion sleeve 10 is so inserted into a bore formed into the lightweight construction panel 100 that its lower end face 113 abuts the lower cover plate 111 in a so-called support zone 114, see FIG. 4. The upper edge 13 of the expansion sleeve 10 is then disposed essentially level with the outer surface 102 of the upper cover plate 101. In the FIGS. 2 and 4, the edge 13 is shown for example slightly below the plane, that is, the level of the outer surface 102 of the upper cover plate 101.

The lower end face 15 of the expansion sleeve 10 may be provided with a cement film or another adhesive coating. The coating may be a cement coating, for example, a micro-sphere coating whose cementing effect is activated only by pressing the end face 15 onto the inner surface 113 of the second cover plate (111).

The expansion sleeve is provided in the upper area of its outer wall, that is, in the area where it is in contact with the upper cover plate 101, once it is installed, with one or several engagement structures. As shown in FIGS. 1 to 4 and 12, there may be for example two circumferential ribs 21. The ribs 21 in this case have the cross-section of a triangular with sides of equal length. The maximum diameter of the ribs 21 is for example a few tenths of a millimeter larger than the inner diameter of the bore 105. The flanks of the ribs 21 enclose for example an angle of 30°. The ribs 21 in this case have a pitch distance of for example 0.7 mm.

With the aid of these ribs 21, the expansion sleeve 10 is—after insertion—firmly retained in the lightweight construction panel 100 even without an application of cement material to the lower end face thereof.

In accordance with FIG. 13, the expansion sleeve includes for example two ribs 22 with different flank angles. In each case, the lower flank is inclined with respect to the center line 9 by about 20° whereas the respective upper flanks are inclined with respect to the center line 9 by an angle of 90°. Both ribs 22 are arranged closely adjacent each other. The flank arrangement shown here facilitates the installation of the expansion sleeve.

In FIGS. 14 and 15, knobs 24 are shown instead of ribs 21, 22. The knobs 24 are arranged for example in two rows on the outer contour of the sleeve next to each other. In circumferential direction, they are spaced from one another by a distance corresponding to about two- to five times the knob foot width. However, the knobs 24 may also be arranged on a zig-zag pattern. Each knob 24 has a semicircular cross-section. Other knob shapes such as pyramid-, cone-, or truncated cone-shapes are also possible.

The variant according to FIGS. 16 and 17 shows a plurality of longitudinal ribs 26 arranged on the outer contour of the sleeve. The longitudinal ribs 26 are in accordance with the shown embodiment about twice as long as the upper cover plate is thick. For example, fifteen longitudinal ribs 26 are equidistantly distributed over the circumference. Each longitudinal rib 26 has for example a cross-section which is defined by lines of equal length, and which increases linearly toward the top so as to reach its maximum at the upper edge 13. This expansion sleeve presses small notches into the wall of the bore 105 so as to prevent rotation of the expansion sleeve.

Alternatively to the expansion sleeves shown, the sleeves may have multi-angled or polygonal outer contours. Also, elliptical cross-sections are possible. Similar shapes may be provided for the opening 16 of the expansion sleeve 10. The bore 16 may also be provided with an internal thread.

The FIGS. 3 and 4 show an expanded expansion sleeve in the form as it is present after installation in a lightweight construction panel 100 and the attachment of a third element 150 in the form of a handle. For installation, the expansion sleeve is inserted into the bore 130 and the handle 150 is held with its threaded bore disposed in front of the bore 115 of the lower cover plate 111. Then a flat head screw 90 is inserted into the bore 16 of the expansion sleeve and is pushed through the bore 15 and finally screwed into the threaded bore 152 of the handle 150.

As soon as the handle 150 contacts with its front face 151, the outer surface 112 of the lower cover plate 111 and the head 91 of the flat head screw 90 abuts the cone-shaped end face 12 of the expansion sleeve, the expansion sleeve is pressed on one hand against the lower cover plate 111 and on the other hand, the upper area of the expansion sleeve is expanded transversely to the center line 9. The expansion effect results from the cooperation between the cone-shaped end face 12 and the shape of the flat head 92 of the flat head screw. The conical upper end face 12 of the expansion sleeve 10 and the screw head form a slide wedge drive. By screwing in the screw, the upper part of the expansion sleeve is expanded elastically or possibly also plastically whereby the expansion sleeve is pressed firmly into engagement with the wall of the bore 105.

After reaching the required screw-in torque, the handle 150 is held in the lightweight construction panel at the same time in two different ways: On one hand, the lower cover plate 111 is clamped between the expansion sleeve and the handle 150 as the clamping sleeve is subjected to an axial pressure. On the other hand, the upper part of the expansion sleeve is radially expanded into firm contact with the walls of the bore 105 while the ribs 21 for example bite into the wall of the bore 105.

When now the handle is subjected to pull forces, the lower as well as the upper cover plates 111, 101 each accommodate part of the pulling force. When, on the other hand, the handle is subjected to forces effective transverse to the longitudinal direction of the screw connection, support is provided for the screw in transverse direction via the thread 95 at the bore 115 and via the screw head 91 at the upper end of the expansion sleeve 10 and consequently at the bore 105.

FIGS. 5 to 7 show an expansion sleeve by which a lightweight construction panel 106 is connected to a transversely extending particle board 160 which forms the third element in a so-called corner joint. To this end, a transverse bore 168 is provided in the particle board 160 and a transverse bolt 165 with a transverse threaded bore 166 is disposed in the transverse bore 162. The threaded bore 166 is in alignment with a screw bore 162. Upon assembly of the two plates or panels 100, 160, the bore 162 of the particle board 160 is in alignment with the bore 16 of the expansion sleeve 10. The engagement force for the two parts is generated in the same way as described earlier in connection with FIGS. 1 to 4.

The expansion sleeve 10 in this case has a special feature. Its lower end face 15 is truncated cone-shaped with the imaginary tip of the cone being disposed on the centerline 9 outside the bore 16. The cone angle is in this case for example 120°. The bore 115 of the lower cover plate 111 is provided with a cone-shaped end 116, which is adapted to the truncated cone-shaped end face 15 of the expansion sleeve.

FIGS. 8 to 10 show an expansion sleeve with an integrated wedge body 31. Also, in this case, a handle 150 is mounted to a lightweight construction panel 100, in this case, however, by means of a screw 90 which has a planar engagement area 93 at the bottom of the screw head.

The expansion sleeve 10 shown consists in this case of a base body 11 and a wedge element 31. The base body 11 has for example essentially the shape of the expansion bodies 10 as represented earlier in FIGS. 1 and 11. The wedge element 31 is a short tube member which, on top, is provided with a flat end face area 32 and is provided at the bottom with an at least generally truncated cone-shaped annular front face 33. The lower front face 33 is outwardly curved that is the imaginary tip of the truncated cone-shaped front face is disposed in the base body bore 16. The cone angle of the lower front face 33 corresponds at least approximately to the cone angle of the upper front face area 12 of the base body 11.

The wedge element 31 is connected to the base body 11 by means of a tubular web 35 or several small individual webs so as to be an integral part thereof. The distance between the front faces 12, 33 is only a few tenth of a millimeter.

In the embodiment of FIG. 9, the base body 11 has in the area of the connection with the tubular webs 35 a face 18 for forming a thin-walled breaking point 19. In the area of the breaking point 19, the web 35 breaks apart when the expansion sleeve and the wedge element 31 are axially compressed, see FIG. 11.

The breaking apart occurs when the screw 90 is tightened. Herein the annular front face 33 of the wedge element 31 abuts the upper front face area 12 and spreads the upper part of the base body 11 apart, see FIG. 11. The wedge element 31 develops during screwing in of the screw, the same forces and effects as the head of the flat head screw 90 used in the previous embodiments.

With the completely assembled connection—handle 150/lightweight construction panel 100—an additional axial abutment connection is provided. The screw head 91 abuts with its planer lower surface 93 additionally the outer upper surface 102 of the upper cover plate 101.

FIG. 3 shows furthermore an anchor installation tool 80. It is of tubular design. With its front area 81, it abuts at least areas of a planar part of the top edge 81 of the front area 12 of the base body 11 whereas the inner wall of its bore 82 abuts the cylindrical outer wall of the wedge element 31. To this end, the diameter of the outer wall of the wedge element 31 is slightly smaller than the outer diameter of the base body 11.

With the anchor installation tool 80, the expansion sleeve can be pressed into the bore 130 without causing damage to the sensitive connection between the base body 11 and the wedge element 31.

FIG. 18 shows an expansion sleeve whose truncated cone-shaped sleeve-like end face 12 has a cone angle which is for example by 5 to 25° smaller than the cone angle of the head 91 of the flat head screw 90, see FIG. 1.

As a result, during mounting of the third element 150, 160, the upper area of the expansion sleeve is clamped into the bore 105 to a greater degree than the lower area.

The principle of the invention is of course not limited to expansion sleeves with at least partially cylindrical outer contours. The expansion sleeve may for example also be designed for cavities which have, at least over sections thereof, rectangular or oval cross-sections. The expansion sleeve then may have two or more bores 16.

It is also possible that the expansion sleeve 10 or the base body are provided in their upper areas with longitudinal axial slots. 

1. An engagement bushing installation for the connection of a lightweight construction panel (100) including first and second spaced cover plates (101, 111) with a support core layer (121) disposed therebetween to a third element (150, 160, 165) by means of a mounting element (90), the bushing having a through bore (16) for accommodating the mounting element (90) in order to attach the third element (150, 160, 165), said lightweight construction panel (100) having a stepped passage (130) for receiving the engagement bushing (10) including a first passage section (105) which extends through the first cover plate (101) and the support core layer (121) and a second passage section of smaller diameter extending through the second cover plate (111), said engagement bushing being disposed in the first passage section of the stepped passage (130) and abutting the second cover plate (111), the diameter of the second passage section being only large enough to accommodate the mounting element (90), the mounting element (90) being provided with a wedge structure for expanding the bushing in the area of the first cover plate (101) into firm radial engagement with the first cover plate (101) upon being mounted to the third element (150, 160, 165) and axially compressing the bushing into firm axial engagement with the second cover plate (111).
 2. An engagement bushing installation as claimed in claim 1, wherein the engagement bushing comprises an essentially tubular sleeve (11) having a planar end face (15) and a truncated cone-shaped front face (12) whose imaginary tip is disposed in the sleeve interior (17) on a centerline (9) of the sleeve (11), said sleeve (11) being radially elastically or plastically expandable in the area of the first cover plate (101).
 3. An engagement bushing installation as claimed in claim 2, wherein the front end area of the sleeve (11) is radially expandable by longitudinal slots formed therein.
 4. An engagement bushing installation as claimed in claim 2, wherein a wedge element (31) is disposed between a head (93) of the mounting element (90) and the tubular sleeve (11), the wedge element (31) having the shape of one of a truncated cone and a pyramid structure.
 5. An engagement bushing installation as claimed in claim 2, wherein the tubular sleeve (11) is in the area of its truncated cone-shaped front end (12) radially elastically deformable by being longitudinally slotted in the front end of the sleeve (11).
 6. An engagement bushing installation as claimed in claim 2, wherein the outer wall of the tubular sleeve (11), at its axial end adjacent the first cover plate (101) where the sleeve engages the wall of the first passage section (105), is provided with engagement projections (21, 24, 26) biting into the wall of the first passage section (105) for preventing relative movement between the sleeve (11) and the lightweight construction panel.
 7. An engagement bushing installation as claimed in claim 6, wherein the engagement projection comprise at least one of circumferential ribs 21, 22 and a plurality of knobs (24).
 8. An engagement bushing installation as claimed in claim 4, wherein the wedge element (31) is formed integrally with the sleeve body (11).
 9. An engagement bushing installation as claimed in claim 8, wherein the wedge element (31) is connected to the sleeve body (11) by way of a web structure (35) forming a breaking point to permit breaking of the wedge element (31) upon mounting of the third element. 